CARC (Claim Adjustment Reason Code)
A CARC is the standardized code on a remittance that states why a payer adjusted a claim line — the payer's stated reason for paying less than billed.
Updated
A Claim Adjustment Reason Code (CARC) is a standardized code returned on the electronic remittance advice that explains why a payer adjusted a claim line — that is, why it paid an amount different from the amount billed. CARCs are maintained as a national code set by X12, so the same code carries the same meaning across payers.
Every CARC is paired with a group code that says who bears the adjusted amount. The group codes are CO (contractual obligation), PR (patient responsibility), OA (other adjustment), and PI (payer-initiated reduction). The group code is what determines whether a balance may be billed to the patient or must be written off.
In practice
The pairing matters more than the code alone: the same adjustment reason under CO and under PR produces opposite next steps — a write-off in one case, a patient statement in the other. Reading the reason without the group code is how balances get billed to patients who do not owe them.
A CARC states the payer's reason; it does not state the root cause. Two claims denied under one code can fail for different upstream reasons, which is why denial work traces the code back to the process that produced it.
Commonly confused with
- RARC: A RARC supplements a CARC with additional explanation; the CARC carries the adjustment reason itself.
- Group code: The group code assigns financial responsibility for the adjusted amount; the CARC says why the adjustment was made.